This invention relates to a series of novel polymeric compounds and to a method for effecting their synthesis. In a more particular aspect, this invention relates to novel polyaromatic amides containing an acetylene moiety along the polymer chain.
Interest in laminates and laminating processes for use in a wide variety of industrial applications has increased considerably in the past few years. Glass fiber laminates, for example, find wide use as structural materials because of their lightweight, high relative strength, and high resistance to corrosion and other damaging effects encountered in an environment subject to extreme fluctuations in temperature and weather. Consequently, a concentrated research effort has evolved in an attempt to develop polymeric materials suitable for use as laminating resins. Such resins must possess a high degree of thermal stability and strength after curing coupled with good solubility characteristics before curing, if they are to be useful for impregnating and bonding the wide variety of laminate materials presently in use.
The research effort referred to above has culminated in the development of several resinous materials that have been found suitable from a stability and strength standpoint. Unfortunately, however, problems have arisen when using such materials due to the evolution of gas during the curing step which occurs after the laminate sheets are impregnated. The curing process which liberates gaseous side products has the deleterious effects of producing voids in the cured laminates which, in turn, substantially weakens the final laminated product.
It becomes obvious, therefore, that thermally stable laminating resins are needed that not only exhibit low melting points and good solubility before curing; but also can be cured without giving off volatile side products. The present invention, therefore, was directed toward providing a solution to the volatility problems previously encountered during the production and curing of laminated structures. As a consequence, it was found that the problems referred to above could be overcome by the development of novel polyaromatic amides curable by Diels-Alder cycloaddition. The resulting polymers contain substituted acetylene units on the polymer chain and not only exhibit good solubility and low melting points before cure coupled with good thermal stability heat and chemical resistance after cure; but are not subject to the liberation of gaseous side products during cure. These polyaromatic amides are susceptible to cure by way of a Diels-Alder cycloaddition reaction because of the functional group on the chain background. This results in an improved heat and chemically stable polymer particularly adapted for use as a laminating resin.